Let's say you started with a 3/8-10 but didn't glue it. Go hit some balls & note the hit. Now take it apart & retrofit a 7/16-14, then note the hit. Now retrofit again for 1/2-20 & note the hit. Other than the slight changes in balance due to weight, i'm betting all three hit exactly the same. This would test only the "A" joint screw, everything else would be exactly the same.
Testing different bolts with the same forearm handle construction could answer several questions. How do you add wood threads into that test? Who wants to do it and share the info?